Are these barbs ready to spawn?

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Neale Monks helps a reader understand if his Tiger Barbs are spawning.

Q: I own a lovely shoal of green Tiger barbs, and while most of them get on with each other just fine, two of them like to lock their mouths together from time to time and spin around in a circle. Sometimes a third one tries to get involved too. Is this a sign of spawning? Should I prepare some kind of breeding site for them?

OLIVER KRAUSE, VIA EMAIL

A: Neale says: It could very easily be the case that your Tiger barbs are spawning, or at least displaying sexual behaviour of some sort. Generally speaking, if the fish are going head-to-head, it might be that they’re a potential pair testing each other out, but it could also be a pair of males pushing each other around as they vie for attention from the females. So, the simplest way to find out what’s happening is to try to sex the fish. If they’re males, then it’s likely aggression, and if they’re one of each sex, then they’re probably forming a pair.

Unfortunately, sexing Tiger Barbs isn’t easy. Unlike some other fish, they aren’t really sexually dimorphic, meaning both sexes have the same basic colour pattern. Females tend to be a little larger and certainly more plump around the abdomen, especially in breeding condition, and that difference tends to be the best way to determine the sex of these fish. Wild males may have stronger colours, but the selective breeding done to create all the various kinds seen in tropical fish shops, such as the popular green variety has made this difference less obvious.

When Tiger barbs are spawning, what you should see is the fish side-by-side, head-to-head, swimming over or through the plants, shedding their sperm and eggs simultaneously. As you can well imagine, they’re trying to get these sex cells as close together as possible, so they can mix together and produce fertilised eggs. Often, the swimming pattern they use is highly distinctive and looks rather laborious, as they wiggle in a jerky manner, seemingly synchronising their movements as they spawn.

If you want to breed Tiger barbs, the main thing is a separate tank that a pair can be put into once they’ve been conditioned. Water chemistry should be relatively soft, and a very gentle water current, like you’d get from a sponge filter, is the order of the day. Aquarists have used many different techniques to breed this species, from naturalistic tanks with dense vegetation, such as Java moss, through to otherwise bare-bottomed tanks lined with marbles which help to prevent the adults eating the eggs. But once spawning has taken place, the adults can be put back into the main tank because they don’t protect the eggs or fry in any way.

The eggs will hatch within a day or two, depending on temperature, and another day or so later the fry will be moving about and ready to feed. They are basically easy to rear, though
like a lot of egg-laying fish, the fry are small, so some sort of tiny live food (typically, infusoria) will be necessary, although you might get lucky using prepared foods, such as Hikari First Bites.